Definition: Given a passage, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.
Input: To investigate if diabetic patients without diabetic retinopathy despite long disease duration have different human leukocyte antigen (HLA) status vs those with an early onset of retinopathy.', 'Retrospective, nonrandomized, masked comparative study. Type 1 diabetic patients with a disease onset before age 30 were recruited to the study. The study population consisted of two groups of diabetic patients: those with normal retinopathy course (retinopathy developed during the first 20 years of diabetes onset) (23 patients) and those with postponed retinopathy (no obvious retinopathy in spite of passing 20 years of diabetes) (19 patients). These groups were matched with regard to level of glycemic control, blood pressure, and lipid profile. A group of 23 healthy patients served as controls. HLA-DQB1 typing of blood samples was done using a polymerase chain reaction with sequence-specific primer (PCR-SSP) method.', 'HLA-DQB1*0201/HLA-DQB1*0501 and HLA-DQB1*0201/HLA-DQB1*0504 haplotypes were more common among type 1 diabetic patients with normal retinopathy course than those with postponed retinopathy (26.1% vs 0.0%; p=0.019). HLA-DQB1*0301 and HLA-DQB1*0304 were less common among those diabetic patients with normal retinopathy course than those with a postponed retinopathy (63.2% vs 34.8%; p=0.067).

Do hLA-DQB1 subtypes predict diabetic retinopathy in patients with type I diabetes mellitus?